The One Cycle Control (OCC) technique for controlling switching circuits is now known. The general technique is described in U.S. Pat. No. 5,278,490. The technique is applied to a PFC (Power Factor Correction) boost converter in U.S. Pat. No. 5,886,586. In the OCC technique, as applied to a PFC boost converter circuit, the output voltage of the converter is sensed, compared to a reference voltage and supplied to an integrator stage, which is reset for each control cycle as set by a system clock. The integrator output is then compared in a comparator to the sensed input current in the converter and the output of the comparator is provided to control a pulse width modulator, whose output controls the boost converter switch. The switch controls the current supplied to the load so that the input ac line current is in phase with the input ac line voltage, i.e., the converter with attached load has a power factor of substantially unity and thus appears purely resistive, resulting in optimum power efficiency as well as reduced harmonics.
Prior to the OCC technique, a multiplier technique was known for PFC in a boost converter circuit. FIG. I depicts a system level block diagram representation of a typical prior art active power factor correction system operating in a fixed frequency, continuous conduction mode (CCM) boost converter topology. The system consists of a continuous conduction mode control integrated circuit 1, based on a multiplier approach, with discrete gate drive circuitry 3 and discrete power switch 5. This control method, based on current mode control, employs the use of a multiplier circuit, input current sensing, input voltage sensing, and output voltage sensing. The analog multiplier creates a current programming signal by multiplying the rectified line voltage by the output of a voltage error amplifier such that the current programming signal has the shape of the input voltage, and average amplitude, which ultimately controls the output voltage of the boost converter. The current loop is programmed by the rectified line voltage such that the input of the converter appears resistive. The output voltage is controlled by changing the average amplitude of the current programming signal. The result is a regulated output voltage and sinusoidal input current in phase and proportional to the input voltage.
The above prior art using the multiplier approach has the disadvantage of high discrete component count and complicated design and development effort required to implement high performance continuous conduction mode power factor correction converters. In addition, it is more difficult to implement a xe2x80x9csingle packagexe2x80x9d design wherein the switch is packaged with the control circuit because of the high component count and numbered pins.
An example of a prior art PFC boost converter using the multiplier technique is shown in U.S. Pat. No. 6,445,600. It would be desirable to provide an integrated circuit for a PFC, CCM boost converter having an integrated switch and OCC controller and which reduces the complexity inherent in a PFC boost converter employing the multiplier technique.
The OCC technique dramatically simplifies the continuous conduction mode (CCM) PFC control function compared to conventional xe2x80x9cmultiplierxe2x80x9d based CCM PFC controllers such as the prior art Unitrode/TI UC3854. The number of package pins are reduced dramatically since the OCC technique does not require line voltage sensing and does not need a complicated multiplier circuit with all its associated external components. The simplicity of this control method thus allows a higher level of integration while allowing use of practical pre-existing power packaging methods for fill integration of the CCM boost PFC controller along with the power switching element all in one package. An example of a packaging method that can be employed is shown in International Publication WO 01/39266 published May 31, 2001.
The present invention thus relates to a single phase, active power factor correction boost converter operating in the continuous conduction mode (CCM). The invention is preferably implemented for continuous conduction mode because this is the most complicated PFC circuit, typically requiring many external components and package pins for the controller. The invention comprises an IC including an active power factor controller based on the OCC technique, integrated gate drive circuitry and integrated power switching device, preferably enclosed in a multi pin power TO-220 or TO-247 package. The IC is packaged with a MOSFEET or IGBT Die preferably using packaging methods in WO 01/39266 above.
According to the invention, there is provided a continuous conduction mode (CCM) power factor corrected boost converter circuit comprising: a rectifier connectable to an ac input and having a rectified dc output provided across a dc bus, an inductor having first and second terminals connected in one leg of the dc bus, a first terminal of the inductor coupled to the output of said rectifier, an integrated circuit comprising a control circuit and a switch controlled by the control circuit, the integrated circuit comprising a housing enclosing the control circuit and switch, the integrated circuit having a power terminal, a ground terminal, a first control input terminal coupled to an output of the converter circuit, a second input terminal coupled to a sensor for sensing current in the dc bus and further having an output terminal connected to the switch and coupled to the second terminal of the inductor, a boost rectifier diode having a first terminal coupled to the output terminal and a second terminal; and a storage capacitor connected to the second terminal of the diode, wherein the control circuit comprises a one cycle control circuit having an integrator reset by a clock signal for each cycle of the clock signal, the integrator receiving as an input a signal provided on said first control input terminal.
The invention also relates to an integrated circuit controller for a CCM PFC boost converter.